Basic composer support

Composer is a fairly new package management tool for php, getcomposer.org

Once merged, you can add the package to the central repository at packagist.org

In the next non-BC release, it might be worth using namespaces seeing as you require >= PHP 5.3 anyway, and trying to follow the [PSR0](https://github.com/php-fig/fig-standards/blob/master/accepted/PSR-0.md) standards for autoloading.